Psychophysiology of false memories in a Deese-Roediger-McDermott paradigm with visual scenes

Abstract

Remembering something that has not in fact been experienced is commonly referred to as false memory. The Deese-Roediger-McDermott (DRM) paradigm is a well-elaborated approach to this phenomenon. This study attempts to investigate the peripheral physiology of false memories induced in a visual DRM paradigm. The main research question is whether false recognition is different from true recognition in terms of accompanying physiological responses.Sixty subjects participated in the experiment, which included a study phase with visual scenes each showing a group of interrelated items in social contexts. Subjects were divided into an experimental group undergoing a classical DRM design and a control group without DRM manipulation. The control group was implemented in order to statistically control for possible biases produced by memorability differences between stimulus types. After a short retention interval, a pictorial recognition phase was conducted in the manner of a Concealed Information Test. Simultaneous recordings of electrodermal activity, respiration line length, phasic heart rate, and finger pulse waveform length were used. Results yielded a significant Group by Item Type interaction, showing that true recognition is accompanied by greater electrodermal activity than false recognition.Results are discussed in the light of Sokolov's Orienting Reflex, the Preliminary Process Theory and the Concealed Information Test. Implications and restrictions of the introduced design features are critically discussed. This study demonstrates the applicability of measures of peripheral physiology to the field of false memory research.

Figure 1. Schematic illustration of all experimental phases.

Overview of experimental phases for both groups. In this example, the broom is a related lure (eg)/related control (cg), the shovel and the bucket are studied items, and the apple is an unrelated item. The study phase contained 13 color pictures showing everyday scenes, the recognition phase contained six items per category: three studied items, two unrelated lures and one related lure/related control. Object pictures were downloaded from the “Creative Commons/Public Domain” licensed homepage “www.openclipart.org” and are vicarious for the copyright protected stimuli used in this study (cp. Appendix S1).

Figure 2. Response behavior in the recognition phase across all item types and groups.

Proportion of trials with a “yes” answer. Error bars represent standard errors of the mean.

Figure 3. Physiological responses to false and true recognition (z-scores).

Overview of electrodermal activity (EDA), respiration line length (RLL), phasic heart rate (pHR) and finger pulse waveform length (FPWL) responses to false and true recognition and their respective control conditions (control group). Error bars represent standard errors of the mean. The physiological measures were z-transformed (for illustration purposes only) for each subject and for each data channel according to , , . All trials except the first trials of each stimulus category were used for the calculation of individual means and standard deviations.